A microelectronic package suitable for high-frequency microelectronic devices includes a base which is at least partially conductive attached to an RF substrate with a cavity formed at its center and a pattern of conductive paths for providing interconnection from the inside to the outside of the package. The base may be metal or ceramic with a metal layer deposited thereon. A sealing cap is attached to the RF substrate by a non-conductive adhesive, such as a polymer adhesive or low temperature seal glass, to seal the package once the microelectronic device has been mounted inside.